The Battle Tower in Galar is the easiest one yet. You're allowed to use Dynamax/Gigantamax every battle, but Leon is the only opponent who will actually use it against you. You're also given pre-made teams that are actually very good to use against them. The only downside is that the BP rewards are slower than Alola's Battle Tree, but it's still way faster than anything up to Generation V.
Where they REALLY take it out on you are the Restricted Battles at the Master Dojo in Isle of Armor. The more of them you clear, the faster they start throwing teams advantageous against the type you select.
If you need any TRs to use, I can give them to you. I always have at least 10 of every TR, and I just replenish my wallet by selling off the ones I don't need, as some of them are worth a lot. (The ones for stuff like Hydro Pump and Gunk Shot sell for 8,000 each, for instance.) I don't consider them being one-time use as that big a hindrance, as I enjoy Max Raid Battles and I've played literally thousands of them, so I actually have quite a surplus.